1. Field
A positive active material and a lithium battery including the same are provided.
2. Description of the Related Art
Demand for lithium secondary batteries for use in portable electronic devices for information communications such as personal digital assistants (PDAs), mobile phones, or notebook computers, electrical bicycles, and electrical vehicles is increasing, and development of small and lightweight electrical devices has lead to commercialization of small lithium batteries that can be charged and discharged with high capacity.
A typical lithium battery includes a positive electrode, a negative electrode, each of which includes an active material enabling intercalation and deintercalation of lithium ions, and an organic electrolytic solution or a polymer electrolytic solution which fills a space between the positive electrode and the negative electrode, and generates an electrical energy due to an oxidation-reduction reaction occurring when lithium ions are intercalated into and/or deintercalated from the positive electrode and the negative electrode.
Lithium batteries have higher voltage and higher energy density than conventional batteries.
However, currently available lithium batteries including lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or lithium nickel cobalt manganese oxide (Li[NiCoMn]O2, Li[Ni1-x-yCoxMy]O2) as a positive active material are unstable because the positive active materials generate a great amount of heat during charging and discharging.
Accordingly, there have been efforts to improve battery stability by adding an additive such as TiO2 and a benzene compound to LiCoO2 that constitutes a positive active material to prevent an excess current and a thermal runaway phenomenon due to the excess current, or by using a small amount of an aromatic compound.
However, such methods are inappropriate for preventing lifetime deterioration and gas formation that occurs by decomposition of an electrolyte during charging and discharging, and ultimately cannot prevent a decrease in stability such as ignition and exploration of batteries although battery stability may be improved in a limited temperature or voltage range.